The objectives of this proposed research are to describe the hemodynamic state of major vascular beds in the various stages of experimental renal hypertension and to attempt to identify the chemical and/or physical factors responsible for these hemodynamics. Measurements will be made in the early (less or greater than 2 weeks' duration) and in the uncomplicated chronic (greater than 4 weeks' duration) stages of either perinephritic or Goldblatt hypertension in dogs under pentobarbital anesthesia. Appropriate normotensive control dogs will also be studied. We will measure blood pressure gradients and flows and calculate resistances in the mesenteric and renal vascular beds and study the effect on these variables of local surgical denervation, vasodilation by supramaximal doses of methacholine, and vasodilation by increased transmural pressures. In addition, we will assess flow- resistance relationships (autoregulation) in these beds. We will also measure volume-pressure relationships (compliance) in temporarily isolated segments of various abdominal veins in situ. Finally, we will bioassay the vasoactivity of renal venous blood in these dogs by pumping venous blood directly into isolated vascular beds (e.g., gracilis muscle) in the same dogs, attempting to identify any vasoactive agents we find in abnormal quantities.